Lubricating oil composition



Patented Feb. 1950 LUBRICATIN G OIL COMPOSITION Darwin E. Badertscher and Charles F. Feasley, Woodbury, and Henry G. Berger, Glen Rock, N. 3., assignors to Socony-Vacuum Oil Company, Incorporated, acorporation of New York No Drawing. Application August 30, 1945, Serial No. 613,704

2 Claims.

This invention has to do withthe treatment of hydrocarbon products such as mineral oils to improve their characteristics, and more specifically to the addition to. petroleum lubricating oils of characterizing agents which improve their ability to resist the deteriorating effect of oxidation.

Moderately refined oils, such as motor oils and other moderately refined lubricating oils normally used under conditions of exposure to oxidation in the presence of metals, oxidize to sludge and/ or acidic oxidation products normally corrosive to the metals which they encounter in use, as, for example, bearing metals in automotive use. It has now been found that stabilization of these oils against such oxidation effects may be conveniently accomplished by addition to the oils of certain materials which substantially retardthe oxidationof the oils, whether or not metal is present, or by the addition of certain other materials which apparently have the ability to inhibit the catalytic effect of metals in promoting oxidation reactions and thus prevent the formation of sludge and/or acidic constituents and the like under normal conditions of use and achieve an equally good practical result, although materials of the latter class may be incapable of inhibiting oxidation of oils in the absence of metals. This invention has to do with stabilizing reaction products which appear to be of this latter class, not heretofore known to be effective for. this purpose, and with oils stabilized by the use of these reaction products.

Recent changes in automotive engine design, tending toward higher bearing pressures, higher rotative speeds, higher engine temperatures, etc., have been concurrent with marked advances in methods of refining lubricant oils for automotive use. The demand for oils having lesser changes in viscosity with temperature change, that is, higher viscosity index, commonly referred to as V. I., has been met by refining lubricants intended for motor oils by certain solvent refining or solvent extraction processes. Certain liquid reagents possess solvent power for hydrocarbons of various types; as, for example, dichlorodiethyl ether, cresylic acid, phenol, chloraniline, chlorophenol, phenetidine, benzyl alcohol, nitrobenzene, benzonitrile, furfural, aniline, benzylacetate, liquid sulphur dioxide, mixtures of liquid sulphur dioxide or aniline with benzol, and the like. Those solvent refining processes are designed to concentrate in the desired lubricant fraction those compounds of a parafiinic nature possessed of the ability to suffer only a small change of viscosity, with changes of temperature, and to reject the compounds of naphthenic nature which do sufier such change of viscosity to a marked degree. These refining processes have provided a supply of an oil of quite desirable general characteristics definitely far superior to any oil previously produced from mixed base or asphaltic crudes, and superior to a like, though lesser, degree over oils previously produced from paraflin base crudes.

It has been found that the solvent refined motor oils referred to above are definitely corrosive to the newer bearing metals referred to above under normal conditions of automotive use, due to oxidation during use, sometimes resulting in bearing failure after only a few thousand miles of normal driving. It is further known that the same reaction, that is, corrosion of alloy-bearing metals such as cadmium-silver, also occurs in good paraifinic base oils which have not been subjected to solvent refining. The higher the V. I. of the lubricating oil, the more pronounced is the tendency to corrosion of the kind referred to above. Generally speaking, the problem is encountered in oils having a V. I. of '75 or higher, and becomes pronounced in oils having a V. I. of to or higher, and very pronounced in oils of V. I. or higher.

It is an object of this invention to prepare novel and valuable ingredients and to combine them with hydrocarbon lubricant oils to produce lubricants having high load bearing capacities, to prepare such ingredients which have good characteristics of stability, and which are less corrosive than ordinary extreme pressure ingredients. Further objects are the provision of methods of preparing lubricants containing these novel characterizing ingredients and methods of lubrication making use of the lubricants so produced.

It is an important object of this invention to provide means for satisfactorily inhibiting or preventing corrosion from taking place to a serious degree particularly in oils of relatively high viscosity index. It is also an object of this 3 invention to provide a substantially non-corrorive motor oil of high V. I. Still another object of the invention is to provide an additive reagent, or ingredient capable of inhibiting the corrosive properties of these oils. The production of solvent refined oils of low corrosive properties under conditions of automotive use is a major object of this invention, as well as the method of production of such oils which combine a relatively high viscosity index with a relatively low tendency to produce such corrosion.

A further object is the provision of a method of lubrication making use of oils containing these novel ingredients.

The present invention is predicated upon the discovery that hydrocarbon oils can be stabilized against the formation of acidic and/or corrosive bodies by oxidation in the presence of metal by the addition to said oils of a relatively small amount of a novel compound represented by the following general formula: a.

wherein R and R are monovalent hydrocarbon groups such as alkyl, alkenyl, cycloalkyl, cycloalkenyl, aralkyl, aralkenyl; alkaryl, alkenaryl, aryl, heteryl, etc., and at least one such group, either R or R is a tertiary alkyl group; R. is a divalent hydrocarbon group of the aforesaid type (R and R or a substituted group thereof such as a halogen-substituted alkyl group, an ether group, a thioether group, etc. A represents a trithiocarbonate group and B represents a trithiocarbonate group. It will be understood from the foregoing that the terms monovalent hydrocarbon group (R' and R and divalent hydrocarbon group (RF) are used generically and include all such groups as those recited above.

Compounds characterized by two tertiary alkyl groups, R and R are outstanding when used in oil in small amounts, as demonstrated hereinafter by representative test data.

Inasmuch as these compounds are believed to be new and novel, they are also contemplated herein as new compositions of matter.

A typical and direct method of preparation of these compounds involves reaction of an organic dihalide and a mixture of a mercaptide and a thiocarbonate salt, as indicated in the following equation:

wherein X is a halogen atom.

ously stirred by an electrically driven stirrer. The reaction mixture was warmed slowly to the reflux temperature, 82-87 0., and was refluxed for 30 hours. The reaction mixture was filtered while warm in order to remove salt which separated therefrom, and the filtrate was separated into two layers, a lower brine layer and an upper isopropyl alcohol layer containing the reaction product. The isopropyl alcohol solution or layer was heated and stirred to remove most of the isopropyl alcohol. The concentrated product was water-washed and thereafter distilled to a maximum temperature of 130" C. at mms., with nitrogen gas being used to sweep out the vapors. The residue, the non-volatile portion, was chilled to 5 C. whereupon yellow crystals separated therefrom. These crystals were removed by filtration thereby providing a filtrate and the yellow crystals. The filtrate contains 44.9 per cent sulphur as against 45.6 per cent sulphur calculated for (I-IaC)3CSCS2CI-IzCH2SC(CI-Ia)3. The yellow solid was recrystallized from Stoddard solvent, washed with petroleum ether and distilled under vacuum to remove said solvent and ether.

The purified yellow solid contained 54.3 per cent sulfur and had a molecular weight of 368-371, as compared with 53.8 per cent sulphur and molecular weight 358, respectively, for

(HsC) aCSCSzCHzCHaSzCSC (CI-b) 3 To demonstrate the effectiveness of compounds of the type contemplated herein, unblended oils and blends thereof containing small amounts of such compounds were subjected to the following corrosion tests: an oil was tested by adding a section of a bearing containing a cadmium-silver alloy surface and weighing about 6 grams and heating it to 175 C. for 22 hours while a stream of air was bubbled against the surfaces of the bearing. The loss in weight of the bearing during this treatment measures the amount of corrosion that has taken place. A sample of the oil containing a characterizing compound was run at the same time as a sample of the straight oil and the loss in weight of the bearing section in the inhibited oil could thus be compared directly with the loss of the section in the uninhibited oil. The oil used consisted of a Pennsylvania neutral and residual stock separately refined by means of Chlorex and then blended to give an SAE 20 motor oil with a specific gravity of 0.872, a fiash point of 435 F., and a Saybolt Universal Viscosity of 318 seconds at 100 F. The results obtained in this test are set forth in the table below:

This method is illustrated by the followin example:

Example An equimolar mixture, 1175 grams, of sodium tertiary butyl mercaptide and sodium tertiary butyl trithiocarbonate was charged into a 22-liter flask with 8 liters of isopropyl alcohol and 375 grams of ethylene dichloride. The reaction mix- The proportion of the characterizing compounds of this invention used in admixture with ordinary hydrocarbon oils may be varied considerably. Generally, concentrations of from about 0.05 per cent to about 5 per cent of the compounds effectively stabilize the oils in which they are used. Further, these characterizing compounds may also be used in oil incombination with other oil-addition agents such, for exture was heated by a hot water bath and vigorample, as pour point depressants, viscosity index improving agents, other'anti-oxidants such, for example, as phenols, amines, etc.

It will be understood that the present invention is not restricted to the details of the .foregoing examples which are presented herein toillustrate the invention, rather the invention is to be construed broadly in the light of the defining language of the appended claims. 9 We claim:- a

1. A mineral oil composition comprising a viscous hydrocarbon fraction and a minor proportion, from about 0.05% to about 5.0%, of a compound represented by the general formula:

where R and R are tertiary lower alkyl groups; R is a divalent lower alkyl group; A is a trithiocarbonate group; and B is a trithiocarbonate group.

2. A mineral oil composition comprising a viscons hydrocarbon fraction and a minor proportion, from about 0.05 to about 5.0% of REFERENCES CITED The following references are of record in the I I file of this patent:

- DARWIN E. BADERTSCHER.

20 CHARLES F. FEASLEY.

HENRY G. BERGER. 

1. A MINERAL OIL COMPOSITION COMPRISING A VISCOUS HYDROCARBON FRACTION AND A MINOR PROPORTION, FROM ABOUT 0305% TO ABOUT 5.0%, OF A COMPOUND REPRESENTED BY THE GENERAL FORMULA: 